Manufacturing method of a magnetic sensor

ABSTRACT

A magnetic sensor comprises magnetoresistive elements and permanent magnet films, which are combined together to form GMR elements formed on a quartz substrate having a square shape, wherein the permanent magnet films are paired and connected to both ends of the magnetoresistive elements, so that an X-axis magnetic sensor and a Y-axis magnetic sensor are realized by adequately arranging the GMR elements relative to the four sides of the quartz substrate. Herein, the magnetization direction of the pinned layer of the magnetoresistive element forms a prescribed angle of 45° relative to the longitudinal direction of the magnetoresistive element or relative to the magnetization direction of the permanent magnet film. Thus, it is possible to reliably suppress offset variations of bridge connections of the GMR elements even when an intense magnetic field is applied; and it is therefore possible to noticeably improve the resistant characteristics to an intense magnetic field.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 10/686,261, filed on Oct. 16, 2003, now U.S. Pat. No.7,170,724, which claims priority to Japanese Patent Application No.2002-304392 and Japanese Patent Application No. 2063-65200, the contentsof each are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to magnetic sensors using magnetoresistiveelements such as giant magnetoresistive (GMR) elements. This inventionalso relates to manufacturing methods for manufacturing magneticsensors.

This application claims priority on Japanese Patent Application No.2002-304392 and Japanese Patent Application No 2003-65200, the contentsof which are incorporated herein by reference.

2. Description of the Related Art

Conventionally, various types of magnetic sensors using magnetoresistiveelements such as giant magnetoresistive (GMR) elements have beendeveloped and reduced to practice.

A typical example of a GMR element comprises a pinned layer in whichmagnetization is pinned in a prescribed direction, and a free layerwhose magnetization direction varies in response to an external magneticfield. That is, when an external magnetic field is applied, the GMRelement presents resistance in response to a relative relationship inmagnetization direction between the pinned layer and free layer;therefore, it is possible to detect the external magnetic field bymeasuring the resistance of the GMR element.

In order to detect minor external magnetic fields at a high accuracy, itis necessary for the aforementioned magnetic sensor to stably maintainthe magnetization direction of each of the magnetized sections of thefree layer to match a prescribed direction (hereinafter, referred to asan initialization direction) under the condition where no externalmagnetic field is applied to the magnetic sensor

In general, a thin-film free layer is formed in a rectangular shape inplan view, so that a long side (e.g., a long axis or a longitudinaldirection) of the rectangular shape is directed to match theaforementioned initialization direction so as to establish shapeanisotropy in which the magnetization directions are aligned to matchthe longitudinal direction By using shape anisotropy, the magnetizationdirections of the magnetized sections of the free layer are aligned tomatch the initialization direction In order to stably restore andmaintain the magnetization directions of the magnetized sections of thefree layer in the initialization direction over a long term after anexternal magnetic field disappears, bias magnet films corresponding topermanent magnets are arranged at both ends of the free layer in thelongitudinal direction, so that a prescribed magnetic field of theinitialization direction is applied to the free layer by the bias magnetfilms.

In magnetoresistance-effect elements (i.e., magnetoresistive elements)of an AMR type, it is necessary to apply bias magnetic fields in orderto increase sensitivities. In order to uniformly apply a bias magneticfield to four magnetoresistive elements, for example, they are inclinedrelative to a substrate by a prescribed angle of 45°. An example of amagnetic sensor in which magnetoresistive elements are inclined relativeto a substrate is disclosed in Japanese Patent Application PublicationNo. Hei 5-126577 (see paragraph [0016], and FIG. 5( a)).

When an external magnetic field, which is relatively large and less thanthe coercive force of a bias magnet film and whose magnetizationdirection is opposite to the initialization direction, is applied to theconventionally-known magnetic sensor, each of the magnetized sections ofthe free layer is changed in magnetization direction, thereafter, whenthe external magnetic field disappears, each of the magnetized sectionsof the free layer cannot be restored and may not match theinitialization direction. This deteriorates the detection accuracy ofthe magnetic sensor for sensing a magnetic field applied thereto.

It is very difficult to form two or more magnetoresistive elements, inwhich the magnetization directions of the pinned layers mutually crosseach other, on a small substrate; therefore, no single chip having sucha configuration has been developed and produced. That is, theconventionally-known magnetic sensor cannot be reduced in size, and itis very difficult to broaden an application range therefor due to arestriction regarding the magnetization direction of the pinned layer.

To cope with the aforementioned situation, it is possible to develop atwo-axis magnetic sensor, using GMR elements, that can be reduced insize and that can be broadened in the application range, which isdisclosed in Japanese Patent Application No. 2001-281703.

FIG. 26 is a plan view showing a two-axis magnetic sensor using GMRelements, wherein a magnetic sensor 101 comprises a quartz substrate 102having a roughly square shape and a prescribed thickness as well asX-axis GMR elements 111 to 114, and Y-axis GMR elements 121 to 124.Herein, all of the X-axis GMR elements 111-114 are formed on the quartzsubstrate 102 and are combined together to form an X-axis magneticsensor for detecting magnetic fields in the X-axis direction, and allthe Y-axis GMR elements 121-124 are formed on the quartz substrate 102and are combined together to form a Y-axis magnetic sensor for detectingmagnetic fields in the Y-axis direction perpendicular to the X-axisdirection.

Two pairs of the X-axis GMR elements 111-112 and 113-114 arerespectively arranged in proximity to the midpoints on two sides of thequartz substrate 102, which cross at a right angle to the X-axis, insuch a way that they are arranged in parallel with each other.Similarly, two pairs of the Y-axis GMR elements 121-122 and 123-124 arerespectively arranged in proximity to the midpoints on two sides of thequartz substrate 102, which cross at a right angle to the Y-axis, insuch a way that they are arranged in parallel with each other.

The X-axis GMR elements 111 to 114 and the Y-axis GMR elements 121 to124 differ from each other in their arrangements on the quartz substrate102 and in their magnetization directions pinned in the pinned layersthereof. With the exception of these points, they are formed in the sameconfiguration.

Therefore, the X-axis GMR element 111 is taken as an example whoseconfiguration is to be described below.

As shown in FIGS. 27 and 28, the X-axis GMR element 111 comprisesband-shaped spin valve films 131, which are arranged in parallel witheach other, and bias magnet films 132, each of which corresponds to athin film of a hard ferromagnetic substance, composed of CoCrPt and thelike, having a high coercive force and a high squareness ratio.

The spin valve films 131 are respectively paired and connected togethervia the bias magnet films 132 at both ends thereof in such a way thatone bias magnet film is arranged at one end of the ‘paired’ spin valvefilms, and the other bias magnetic film is arranged at the other end ofthe ‘adjacent paired’ spin valve films. In short, the spin valve films131 are connected together via the bias magnet films 132 in a zigzagmanner.

As shown in FIG. 29, the spin valve film 131 is formed in a sequentiallamination of various layers on the quartz substrate 102, namely: a freelayer F; a conductive spacer layer S, composed of Cu, having a filmthickness of 2.4 nm (or 24 Å); a pinned layer PD composed of CoFe; apinning layer PN composed of PtMn; and a capping layer C made of a thinmetal film composed of titanium (Ti), tantalum (Ta), and the like.

The free layer F is changed in magnetization direction in response tothe direction of an external magnetic field applied thereto, and it isformed by a CoZrNb amorphous magnetic layer 131 a having a filmthickness of 8 nm (or 80 Å), a NiFe magnetic layer 131 b having a filmthickness of 3.3 nm (or 33 Å) that is laminated on the CoZrNb amorphousmagnetic layer 131 a, and a CoFe layer 131 c whose film thicknessapproximately ranges from 1 nm to 3 nm (or 10 Åto 30 Å) that islaminated on the NiFe magnetic layer 131 b.

In order to maintain single-axis anisotropy of the free layer F, a biasmagnetic field is applied to the free layer F by the bias magnet film132 in the Y-axis direction shown in FIG. 27.

The spacer layer S is a thin metal film composed of Cu or a Cu alloy.

Both of the CoZrNb amorphous magnetic layer 131 a and the NiFe magneticlayer 131 b are formed from soft ferromagnetic substances. In addition,the CoFe layer 131 c blocks Ni diffusion of the NiFe magnetic layer 131b and Cu diffusion of the spacer layer S.

The pinned layer PD is formed by a CoFe magnetic layer 131 d having afilm thickness of 2.2 nm (or 22 Å). The CoFe magnetic layer 131 d isbacked by an antiferromagnetic film 131 e, which will be describedlater, in a switched connection manner so that the magnetizationdirection thereof is subjected to pinning (or anchoring) in the negativedirection of the X-axis.

The pinning layer PN is formed by the antiferromagnetic film 131 ehaving a film thickness of 24 nm (or 240 Å) laminated on the CoFemagnetic layer 131 d, wherein the antiferromagnetic film 131 e iscomposed of a PtNm alloy including Pt at 45-55 mol %. When a magneticfield is applied in the negative direction of the X-axis, theantiferromagnetic film 131 e is changed to an ordered lattice.

Hereinafter, the combination of the pinned layer PD and the pinninglayer PN will be generally called a pin layer.

All of the other X-axis GMR elements 112-114 and the Y-axis GMR elements121-124 have the same configuration as the X-axis GMR element 111described above; hence, the detailed descriptions thereof will beomitted.

Next, a description will be given with respect to the magneticproperties (or magnetic characteristics) of the X-axis GMR elements111-114 and the Y-axis GMR elements 121-124.

FIG. 30 shows a graph regarding variations of resistance relative to themagnitude of an external magnetic field applied to the X-axis GMRelement 111. Herein, ‘solid’ curves represent hysteresis characteristicsrelative to variations of the external magnetic field in the X-axis, inwhich the resistance varies approximately proportional to the externalmagnetic field in a prescribed range between −Hk and +Hk, but theresistance is maintained substantially constant in both of the otherranges outside of the prescribed range. In addition, ‘dotted’ curvesrepresent characteristics relative to variations of the externalmagnetic field in the Y-axis, in which the resistance is maintainedsubstantially constant.

In FIG. 26, magnetization directions of pinned layers adapted to theX-axis GMR elements 111-114 and the Y-axis GMR elements 121-124 areshown by arrows, which are directed opposite to each other.

That is, both of the X-axis GMR elements 111 and 112 have the samemagnetization direction of the pinned layer that is pinned by thepinning layer along the negative direction of the X-axis.

Both of the X-axis GMR elements 113 and 114 have the same magnetizationdirection of the pinned layer that is pinned by the pinning layer alongthe positive direction of the X-axis.

In addition, both of the Y-axis GMR elements 121 and 122 have the samemagnetization direction of the pinned layer that is pinned by thepinning layer along the positive direction of the Y-axis.

Both of the Y-axis GMR elements 123 and 124 have the same magnetizationdirection of the pinned layer that is pinned by the pinning layer alongthe negative direction of the Y-axis.

The aforementioned X-axis magnetic sensor is constituted by arrangingthe X-axis GMR elements 111-114 in a full bridge connection as shown inFIG. 31, wherein arrows accompanied with blocks show magnetizationdirections of pinned layers pinned by pinning layers. In theaforementioned constitution, a dc power source is used to apply voltageVxin+ (e.g., 5 V) at one terminal and to apply voltage Vxin− (e.g., 0 V)at the other terminal, whereby Vxout+ appears at a terminal H that isderived from the connection between the X-axis GMR elements 111 and 113,and Vxout− appears at a terminal L that is derived from the connectionbetween the X-axis GMR elements 112 and 114. Herein, it is possible toextract a potential difference (or a voltage difference) (Vxout+−Vxout−)as an output voltage Vxout.

In short, the X-axis magnetic sensor presents characteristics relativeto variations of an external magnetic field in the X-axis, in which, asshown by the solid curves in FIG. 32, the output voltage Vxout thereofis changed substantially proportional to the external magnetic field ina prescribed range between −Hk and +Hk, and it is maintainedsubstantially constant in other ranges outside of the prescribed range.

In addition, the output voltage Vout is substantially maintained at 0 Vrelative to variations of the external magnetic field in the Y-axis,which is shown by the dotted curves in FIG. 32.

Similar to the aforementioned X-axis magnetic sensor, the Y-axismagnetic sensor is constituted by arranging the Y-axis GMR elements121-124 in a full bridge connection as shown in FIG. 33. In thisconstitution, a dc power source is used to apply voltage Vyin+ (e.g., 5V) at one terminal and to apply voltage Vyin− (e.g., 0 V) at the otherterminal, whereby Vyout+ appears at a terminal H that is derived fromthe connection between the Y-axis GMR elements 122 and 124, and Vyout−appears at a terminal L that is derived from the connection between theY-axis GMR elements 121 and 123. Herein, it is possible to extract apotential difference (Vyout+−Vyout−) as an output voltage Vyout.

In short, the Y-axis magnetic sensor presents hysteresis characteristicsrelative to variations of an external magnetic field in the Y-axis, inwhich, as shown by dotted curves in FIG. 34, the output voltage Vyoutthereof is changed substantially proportional to the external magneticfield in a prescribed range −Hk and +Hk, and it is maintainedsubstantially constant in other ranges outside of the prescribed range.

In addition, the output voltage Vyout is substantially maintained at 0 Vrelative to variations of the external magnetic field in the Y-axis,which is shown by the solid curves in FIG. 34.

Next, a description will be given regarding a manufacturing method ofthe magnetic sensor 101.

As shown in FIG. 35, a plurality of island-like regions, correspondingto films M which contribute to formation of individual GMR elements, areformed on the surface of a quartz glass 141 having a rectangular shape.When the quartz glass 141 is subjected to a cutting process along breaklines B and is thus divided into individual quartz substrates 102, thefilms M are arranged at prescribed positions to match the X-axis GMRelements 111-114 and the Y-axis GMR elements 121-124. In addition,alignment marks (i.e., positioning marks) 142 are formed on four cornersof the quartz glass 141, wherein each of them is formed in a roughlyrectangular shape from which a cross-shaped region is removed.

Next, there are provided a plurality of rectangular metal plates 144,each of which, as shown in FIGS. 36 and 37, has a plurality of throughholes 143 having square openings, which are formed and regularlyarranged in a lattice-like manner. In addition, permanent magnets 145,each having a rectangular parallelopiped shape whose cross-sectionalshape substantially matches the opening shape of each of the throughholes 143, are respectively inserted into the through holes 143 in sucha way that the upper end surfaces of the permanent magnets 145respectively inserted into the through holes 143 are all arranged in thesame plane substantially in parallel with the surface of the metal plate144, wherein the ‘adjacent’ permanent magnets 145 differ from each otherin polarity.

Next, there is provided a plate 151, which is shown in FIG. 38, made ofa transparent quartz glass having substantially the same shape as themetal plate 144. In addition, cross-shaped alignment marks (orpositioning marks) 152 are formed on the four corners of the plate 151to cooperate with the aforementioned alignment marks 142 of the quartzglass 141, thus establishing positioning between the quartz glass 141and the plate 151. In addition, a plurality of alignment marks 153, eachof which matches the contour shape of each of the permanent magnets 145,are formed in conformity with the positions of the through holes 143 ofthe metal plate 144.

The upper end surfaces of the permanent magnets 145 are adhered to thelower surface of the plate 151 by use of a prescribed adhesive. At thistime, a prescribed positioning is established between the metal plate144 (holding the permanent magnets 145) and the plate 151 by use of thealignment marks 153.

Thereafter, the metal plate 144 is removed from the lower side of theplate 151. Thus, it is possible to produce a magnet array in which thepermanent magnet 145 are arranged on the plate 151 in a lattice-likemanner and in which the ‘adjacent’ permanent magnets differ from eachother in polarity.

As shown in FIG. 40, the quartz glass 141 is brought into contact withthe plate 151 in such a way that the aforementioned films M come intocontact with the upper surface of the plate 151. Herein, the prescribedpositioning is established between the quartz glass 141 and the plate151 by mutually matching the alignment marks 142 with the alignmentmarks 152. Then, fixing members 155 such as clips are used to fix thequartz glass 141 and the plate 151 together.

In the aforementioned state, as shown in FIG. 41, magnetic forces areformed in directions from the N pole of one permanent magnet 145 towardsthe S poles of adjacent permanent magnets 145. Therefore, as shown inFIG. 42, magnetic forces are applied to the films M, which are arrangedto encompass one permanent magnet 145, in four directions, that is, thepositive direction of the Y-axis, the positive direction of the X-axis,the negative direction of the Y-axis, and the negative direction of theX-axis.

The quartz glass 141 and the plate 151 fixed together by the fixingmembers 155 are subjected to a heat treatment for four hours at aprescribed temperature ranging from 250° C. to 280° C., for example.Thus, it is possible to order the pinning layers and to pin the pinnedlayers of the GMR elements. The quartz glass 141 and the plate 151 areseparated from each other, and passivation films and polyimide films areformed for the purpose of protection; then, the quartz glass 141 issubjected to cutting on break lines B. Thus, the magnetic sensor 101 isproduced.

Compared with the conventionally-known magnetic sensor in whichmagnetoresistive elements of the AMR type are inclined at 45° relativeto the substrate, the aforementioned two-axis magnetic sensor has anadvantage which allows magnetic measurement on geomagnetic levelswithout using bias magnetic fields; however when applied with an intensemagnetic field, the magnetized states thereof are unexpectedly changedso as to cause unwanted offsets in the bridge configurations of the GMRelements.

To cope with the aforementioned drawback, it is possible to suppressoffset variations against the influence of an intense magnetic field byattaching permanent magnets to both ends of the GMR elements.Specifically, a relatively great magnetic field that is greater than thecoercive force Hc of the permanent magnet is applied to the GMR elementin the longitudinal direction, i.e., longitudinal direction of the freelayer, so that the free layer is being initialized at the same time thatthe permanent magnet is attached so as to cause magnetization. Herein,it is possible to use the aforementioned magnet array, which is used inan ordering heat treatment of pin layers, in this method.

In the aforementioned method, however, it is necessary to apply amagnetic field in a direction perpendicular to the longitudinaldirection of the GMR element in the ordering heat treatment, and it isalso necessary to apply a magnetic field whose magnetism is identical tothat of the permanent magnet in the longitudinal direction of the GMRelement. Herein, magnetic fields of different directions are required inthe aforementioned steps.

In the magnet array, under the ordering heat treatment, each of thepermanent magnets should be arranged such that the center of gravitythereof is coincident with the center of each cell on the quartz glass,and when each of them is arranged to cause magnetization, it should beshifted in position so that the center of gravity thereof is coincidentwith each of the four corners of the quartz glass. This may causepositional deviations, which in turn cause the initialization directionto be shifted and thus deteriorates the measurement accuracy. When theaforementioned magnetic sensor is used under the influence of an intensemagnetic field, offsets become easy to vary.

As described above, the aforementioned two-axis magnetic field may havean advantage in the reduction of the hysteresis characteristics of theGMR elements under the influence of a weak magnetic field; however, thiswould not sufficiently contribute to the stability of the offsets.

Magnetized states that are unexpectedly moved under the influence of anintense magnetic field may be restored to the original ones by applyingan initialization magnetic field to form thin film coils, which areembedded beneath the GMR elements. However, this method does notsufficiently contribute to the stability of the offsets.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a magnetic sensor that canbe controlled in offset variations, regardless of the influence of anintense magnetic field applied thereto, so as to improve the magneticcharacteristics with respect to the intense magnetic field.

It is another object of the invention to provide a manufacturing methodfor manufacturing the aforementioned magnetic sensor.

A magnetic sensor of this invention comprises magnetoresistive elementsand permanent magnet films, which are combined together to form GMRelements formed on a quartz substrate having a square shape, wherein thepermanent magnet films are paired and connected to both ends of themagnetoresistive elements. That is, the magnetic sensor detects themagnitude of an external magnetic field applied thereto in two axialdirections, so that an X-axis magnetic sensor and a Y-axis magneticsensor are realized by adequately arranging the GMR elements relative tothe four sides of the quartz substrate. In particular, this invention ischaracterized in that the magnetization direction of the pinned layer ofthe magnetoresistive element forms a prescribed angle of 45° relative tothe longitudinal direction of the magnetoresistive element.Alternatively, the magnetization direction of the pinned layer of themagnetoresistive element forms a prescribed angle of 45° relative to themagnetization direction of the permanent magnet film. Thus, it ispossible to reliably suppress offset variations of bridge connections ofthe GMR elements even when an intense magnetic field is applied; and itis therefore possible to noticeably improve the resistantcharacteristics to an intense magnetic field.

A manufacturing method of the magnetic sensor of this invention ischaracterized in that an ordering heat treatment is performed byarranging a substrate on a magnet array in which a plurality ofpermanent magnets are arranged such that adjoining permanent magnetsdiffer from each other in polarity, wherein the permanent magnets arepositioned respectively or selectively on the four corners of a cell(corresponding to the quartz substrate) within the substrate, which isthen heated. Alternatively, the ordering heat treatment is performed byarranging the substrate such that the magnetization direction of thepinned layer of the magnetoresistive element matches the diagonal lineof the substrate, which is then heated, wherein the permanent magnetfilms are adequately magnetized using a magnet array in which adjoiningpermanent magnets differ from each other in polarity.

Thus, it is possible to produce the magnetic sensor, in which themagnetization direction of the pinned layer of the magnetoresistiveelement forms a prescribed angle of 45° relative to the magnetizationdirection of the permanent magnet film, by simple processes with ease.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, aspects, and embodiments of the presentinvention will be described in more detail with reference to thefollowing drawings, in which:

FIG. 1 is a plan view showing a magnetic sensor using GMR elements inaccordance with a first embodiment of the invention;

FIG. 2 is a plan view showing a quartz substrate arranging GMR elementsfor use in the manufacture of the magnetic sensor of the firstembodiment;

FIG. 3 is a partial plan view showing a metal plate for use in themanufacture of the magnetic sensor of the first embodiment;

FIG. 4 is a partial plan view showing a metal plate for use in themanufacture of a conventional magnetic sensor;

FIG. 5 is a plan view showing sensing directions F1 and F2 with regardto X-axis and Y-axis GMR elements incorporated in the magnetic sensor ofthe first embodiment;

FIG. 6 is a plan view showing the arrangements of GMR elements andpermanent magnets on the quartz substrate for use in the manufacture ofthe magnetic sensor of the first embodiment;

FIG. 7 is a block diagram simply showing a bridge connection establishedamong the X-axis GMR elements;

FIG. 8 is a block diagram simply showing a bridge connection establishedamong the Y-axis GMR elements;

FIG. 9 is a graph showing the magnetic characteristics of the X-axis andY-axis GMR elements incorporated in the magnetic sensor of the firstembodiment;

FIG. 10 is a graph showing the magnetic characteristics of the X-axisand Y-axis GMR elements incorporated in the conventional magneticsensor;

FIG. 11A is a cross sectional view showing a combination of a substrateand a metal plate for holding permanent magnets in the manufacture ofthe magnetic sensor;

FIG. 11B is a cross sectional view in which the substrate and the metalplate are fixed together using fixing members;

FIG. 12 is a plan view showing a magnetic sensor in accordance with asecond embodiment of the invention;

FIG. 13 is a plan view showing a magnet array for use in the magneticsensor of the second embodiment, in which a plurality of bar magnets arearranged in parallel;

FIG. 14A is a cross sectional view showing a silicon substrate in whichslots are formed in parallel with each other in the manufacture of amodified example of a magnet array for use in the magnetic sensor of thesecond embodiment;

FIG. 14B is a cross sectional view showing the magnet array in which barmagnets are respectively inserted into the slots of the siliconsubstrate;

FIG. 15 is a partial perspective view in cross section showing anarrangement of the bar magnets of different polarities inserted into theslots of the silicon substrate;

FIG. 16 is a plan view showing the positional relationships between thebar magnets of different polarities and a quartz substrate derived froma quartz glass;

FIG. 17A is a cross sectional view showing a substrate in which slotsare formed in parallel with each other in the manufacture of a modifiedexample of a magnet array for use in the magnetic sensor of the secondembodiment;

FIG. 17B is a cross sectional view showing the magnet array in which barmagnets are respectively inserted into the slots of the substrate;

FIG. 18 is a partial perspective view in cross section showing anarrangement of the bar magnets of the same polarity inserted into theslots of the substrate;

FIG. 19 is a plan view showing the positional relationships of the barmagnets of the same polarity and a quartz substrate;

FIG. 20 is a plan view showing a quartz glass on which GMR elements andbar magnets are arranged in the manufacture of a magnetic sensor inaccordance with a second embodiment of the invention;

FIG. 21 is a plan view showing an arrangement of the GMR elements of themagnetic sensor of the second embodiment in connection with X-axis andY-axis sensing directions;

FIG. 22 is a plan view showing an arrangement of permanent magnetsrelative to the GMR elements formed on the quartz substrate for use inthe manufacture of the magnetic sensor of the second embodiment;

FIG. 23 is a plan view showing a magnetic sensor in accordance with afourth embodiment of the invention;

FIG. 24 is a plan view showing an arrangement of GMR elements on aquartz glass in the manufacture of the magnetic sensor of the fourthembodiment;

FIG. 25 is a plan view showing sensing directions actualized by themagnetic sensor of the fourth embodiment;

FIG. 26 is a plan view showing a two-axis magnetic sensor using GMRelements;

FIG. 27 is a plan view showing the configuration of a GMR element foruse in the two-axis magnetic sensor;

FIG. 28 is a cross sectional view taken along line A-A in FIG. 27;

FIG. 29 is a cross sectional view diagrammatically showing theconstitution of a spin valve film used in the GMR element shown in FIG.27;

FIG. 30 is a graph showing the magnetic characteristics of the GMRelement;

FIG. 31 is a block diagram simply showing a full bridge connection ofGMR elements adapted to an X-axis magnetic sensor;

FIG. 32 is a graph showing the magnetic characteristics of the X-axismagnetic sensor;

FIG. 33 is a block diagram simply showing a full bridge connection ofGMR elements adapted to a Y-axis magnetic sensor;

FIG. 34 is a graph showing the magnetic characteristics of the Y-axismagnetic sensor;

FIG. 35 is a plan view showing the formation of GMR element films on aquartz glass, which is used in the manufacture of the two-axis magneticsensor;

FIG. 36 is a plan view showing a metal plate arranging permanentmagnets, which is used to manufacture the two-axis magnetic sensor;

FIG. 37 is a cross sectional view taken along line B-B in FIG. 36;

FIG. 38 is a plan view showing a transparent quartz glass plate for usein the manufacture of the two-axis magnetic sensor;

FIG. 39 is a cross sectional view showing that permanent magnets of amagnet array are adhered to the transparent quartz glass plate;

FIG. 40 is a cross sectional view showing that a quartz glass and thetransparent quartz glass plate holding the permanent magnets are fixedtogether via fixing members;

FIG. 41 is a perspective view diagrammatically showing the directions ofmagnetic forces applied among permanent magnets, which are arrangedadjacent to each other in the magnet array;

FIG. 42 is a plan view showing the method in which thin magnetic filmsare magnetized under influences of permanent magnets in the manufactureof the two-axis magnetic sensor; and

FIG. 43 is a table showing the experimental results upon comparisonbetween the embodiments and a comparative example corresponding to atwo-axis magnetic sensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention will be described in further detail by way of exampleswith reference to the accompanying drawings.

1. First Embodiment

FIG. 1 is a plan view showing a two-axis magnetic sensor using GMRelements in accordance with a first embodiment of the invention.

That is, a magnetic sensor I comprises a quartz substrate 2 having aprescribed thickness and a roughly square shape, X-axis GMR elements 11to 14 that are formed on the quartz substrate 2 so as to form an X-axismagnetic sensor for detecting magnetic fields in an X1-axis direction,and Y-axis GMR elements 21 to 24 that are formed on the quartz substrate2 so as to form a Y-axis magnetic sensor for detecting magnetic fieldsin a Y1-axis direction, which is perpendicular to the X1-axis direction.Specifically, the sensing direction of the X-axis magnetic sensor liesin the X1-axis direction that is formed 45° relative to the X-axisdirection, and the sensing direction of the Y-axis magnetic sensor liesin the Y1-axis direction that is formed 45° relative to the Y-axisdirection.

In the above, it is possible to substitute silicone for the material ofthe quartz substrate 2.

In FIG. 1, the X-axis GMR elements 11 to 14 are paired and respectivelyarranged in proximity to the midpoints on two sides of the quartzsubstrate 2, which are perpendicular to the X-axis, in such a way thatthey are arranged in parallel with each other. Similarly, the Y-axis GMRelements 21 to 24 are paired and respectively arranged in proximity tothe midpoints on the other two sides of the quartz substrate 2, whichare perpendicular to the Y-axis, in such a way that they are arranged inparallel with each other.

Each of the X-axis GMR elements 11-14 and the Y-axis GMR elements 21-24is constituted by a plurality of band-shaped magnetoresistive elements31, which are composed of spin valve films arranged in parallel witheach other, and a plurality of permanent magnet films 32, which areconnected with both ends of the magnetoresistive elements 31 inlongitudinal directions and which are composed of thin films of a hardferromagnetic substance such as CoCrPt having a high coercive force anda high squareness ratio, wherein a prescribed angle of 45° is formedbetween the longitudinal direction of the magnetoresistive element 31and the longitudinal direction of the adjoining permanent magnet film32.

In addition, each of the magnetoresistive elements 31 is arranged insuch a way that the longitudinal direction thereof forms a prescribedangle of 45° relative to the proximate side of the quartz substrate 2.In addition, each of the permanent magnet films 32 is arranged in such away that the longitudinal direction thereof is in parallel with theproximate side of the quartz substrate 2, wherein the permanent magnetfilm 32 arranged at one end of the magnetoresistive element 31 differsfrom the other permanent magnet film 32 arranged at the other end of themagnetoresistive element 31 in the distance measured from the proximateside of the quartz substrate 2.

The magnetization direction of the free layer of the magnetoresistiveelement 31 lies in the longitudinal direction thereof, and themagnetization direction of the permanent magnet film 32 also lies in thelongitudinal direction thereof. Hence, a prescribed angle of 45° isformed between the magnetization direction of the free layer of themagnetoresistive element 31 and the magnetization direction of thepermanent magnet film 32.

In addition, the magnetization direction pinned in the pinned layer ofthe magnetoresistive element 31 is formed 45° relative to thelongitudinal direction of the magnetoresistive element 31. That is, thedirection of a magnetic field applied in the ordering heat treatment isformed 45° relative to the longitudinal direction of themagnetoresistive element 31.

Furthermore, the magnetization direction pinned in the pinned layer ofthe magnetoresistive element 31 is identical to the magnetizationdirection of the permanent magnet film 32. That is, the direction of amagnetic field applied in the ordering heat treatment is identical tothe direction of a magnetic field applied to magnetize themagnetoresistive element 31.

The structure of the spin valve film of the magnetoresistive element 31is identical to the foregoing structure of the spin valve film 131 usedfor the X-axis GMR elements 111-114 and the Y-axis GMR elements 121-124;hence, the detailed description thereof will be omitted.

The present embodiment is characterized in that each of the X-axis GMRelements 11-14 and the Y-axis GMR elements 21-24 defines themagnetization direction of the pinned layer PD of the magnetoresistiveelement 31 so as to be identical to the magnetization direction of thepermanent magnet film 32.

In addition, the magnetoresistive element 31 and the permanent magnetfilm 32 are connected together in such a way that the longitudinaldirection of the free layer F is inclined against the longitudinaldirection of the permanent magnet film 32 by 45°.

Next, a manufacturing method of the magnetic sensor 1 will be describedin detail.

Similar to the foregoing magnetic sensor 101, a plurality of islandregions corresponding to the permanent magnet films 32, which areconnected with GMR elements respectively, are arranged and formed on thesurface of a rectangular-shaped quartz glass 41. As shown in FIG. 2,films N corresponding to the permanent magnet films 32 define regions Mfor arranging the GMR elements, so that when the quartz glass 41 issubjected to a cutting process along break lines B and is thus dividedinto individual quartz substrates 2, the regions M are aligned to matchprescribed positions of the X-axis GMR elements 11-14 and the Y-axis GMRelements 21-24.

In addition, alignment marks (not shown) are formed on the four cornersof the quartz glass 41. After formation of the permanent magnet films32, a film (or films) for forming the GMR elements is formed on theoverall surface of the quartz glass 41.

Next, as shown in FIG. 3, there is provided a metal plate 44 in which aplurality of through holes 43 each having a square-shaped opening areformed in a lattice-like manner. A plurality of permanent magnets 45each having a rectangular parallelopiped shape whose cross-sectionalshape substantially matches the opening of the through hole 43 arerespectively inserted into the through holes 43 in such a way that theupper end surfaces thereof are aligned substantially in the same planein parallel with the surface of the metal plate 44, and the ‘adjoining’permanent magnets 45 differ from each other in polarity.

Next, there is provided a plate made of a transparent quartz glass,which has substantially the same shape as the metal plate 44. Similar tothe foregoing plate 151 shown in FIG. 38, alignment marks 153 are formedat prescribed positions in correspondence with the through holes 43.

In the above, the foregoing alignment marks 152 are formed at the fourcorners of the plate in order to establish prescribed positioningbetween the quartz glass 41 and the plate, wherein in the presentembodiment compared with the foregoing example shown in FIG. 38, each ofthem is shifted in position in both the negative direction of the X-axisand the negative direction of the Y-axis by half of the length of theside of the quartz substrate 2, in other words, it is shifted by a halfpitch. Of course, it is possible to form both of the foregoing alignmentmarks 152 and the half-pitch shifted alignment marks on the plate.

A magnet array is constituted by arranging the permanent magnets 45 in alattice-like manner, wherein the upper end surfaces of the permanentmagnets 45 are adhered to the lower surface of the plate by use of aprescribed adhesive. At this time, the prescribed positioning isestablished between the permanent magnets 45 and the plate by use of theaforementioned alignment marks 153.

Next, the metal plate 44 is removed, so that the magnet array isproduced in which the permanent magnets 45 are arranged in alattice-like manner in such a way that the adjoining permanent magnets45 differ from each other in polarity.

The quartz glass 41 and the plate are combined in such a way that thefilms M are brought into contact with the upper surface of the plate.Herein, the prescribed positioning is established between the quartzglass 41 and the plate by mutually matching half-pitch shifted alignmentmarks of the plate with the foregoing alignment marks of the quartzglass 41. Thus, it is possible for the four corners of the quartzsubstrate 2, which forms an individual cell derived from the quartzglass 41, to coincide with the centers of gravity of the permanentmagnets 45 respectively Thereafter, the quartz glass 41 and the plateare fixed together by using a plurality of fixing members such as clips.

Next, the pinning layer PN of the magnetoresistive element 31 issubjected to an ordering heat treatment, wherein the pinned layer PD issubjected to pinning as well.

Under the condition where the quartz glass 41 and the plate are fixedtogether, as shown in FIG. 2, permanent magnets 45 are arranged at thefour corners of the quartz substrate 2, which is divided by thesubsequent cutting process, in such a way that adjacent permanentmagnets differ from each other in polarity. Therefore, a magnetic fieldis caused to occur in a direction from the N pole of the permanentmagnet 45 to the S pole of the other ‘adjacent’ permanent magnet 45,wherein it is directed in parallel to each side of the quartz substrate2. That is, a magnetic field is applied to each film M in a directionthat is inclined by 45° with respect to the longitudinal direction ofthe pin layer of the magnetoresistive element 31.

Next, the quartz glass 41 and the plate, which are fixed together usingthe fixing members, are subjected to a heat treatment for four hoursunder vacuum at a prescribed temperature ranging from 250° C. to 280° C.

Thus, it is possible to complete an ordering heat treatment on thepinning layer PN within the pin layer of the magnetoresistive element 31belonging to each of the X-axis GMR elements 11-14 and the Y-axis GMRelements 21-24. Herein, the pinned layer PD is subjected to pinning in aswitched connection manner.

Thereafter, the X-axis GMR elements 11-14 and the Y-axis GMR elements21-24 are subjected to patterning and are thus arranged in prescribedpatterns, wherein the permanent magnets 32 are adequately connectedtogether in a zigzag manner.

The aforementioned magnetic sensor 1 has an X-axis sensing direction F1and a Y-axis sensing direction F2 with respect to the pin layers of themagnetoresistive elements 31 as shown in FIG. 5, wherein the X-axissensing direction F1 is inclined by 45° relative to one side of thequartz substrate 2, and the Y-axis sensing direction F2 is inclined by45° relative to the other side of the quartz substrate 2.

Next, the same magnet array is used without changing the positionthereof, so that, as shown in FIG. 6, the permanent magnet films 32 arearranged to start magnetization thereby under the condition where thepermanent magnets 45 are arranged such that the centers of gravitythereof coincide with the four corners of the quartz substrate 2respectively. Herein, magnetization directions of the permanent magnets32 are set to be identical to the magnetization directions of the pinnedlayers PD of the magnetoresistive elements 31. Therefore, the pinnedlayers PD of the magnetoresistive elements 31 are reliably subjected topinning; hence, it is possible to produce the magnetic sensor 1 that isinfluenced by magnetization of the permanent magnets 32.

FIG. 7 shows a bridge connection established among the X-axis GMRelements 11-14 forming the X-axis magnetic sensor incorporated in themagnetic sensor 1, wherein reference symbol X₁designates the X-axis GMRelements 11 and 12, and X₂ designates the X-axis GMR elements 13 ad 14.All the sensing directions of the X-axis GMR elements 11-14 match theaforementioned X-axis sensing direction F1 shown in FIG. 5; hence, whenan external magnetic field is applied in a direction opposite to theX-axis sensing direction F1, a terminal ‘L’ becomes higher in potentialcompared with another terminal ‘H’.

FIG. 8 shows a bridge connection established among the Y-axis GMRelements 21-24 forming the Y-axis magnetic sensor incorporated in themagnetic sensor 1, wherein reference symbol Y₁ designates the Y-axis GMRelements 21 and 22, and Y₂ designates the Y-axis GMR elements 23 and 24.All the sensing directions of the Y-axis GMR elements 21-24 match theaforementioned Y-axis sensing direction F2 shown in FIG. 5; hence, whenan external magnetic field is applied in a direction opposite to theY-axis sensing direction F2, a terminal ‘L’ becomes higher in potentialcompared with another terminal ‘H’.

FIG. 9 shows the magnetic characteristics of the X-axis GMR elements11-14 and the Y-axis GMR elements 21-24 incorporated in the magneticsensor 1, and FIG. 10 shows the magnetic characteristics of the X-axisGMR elements 111-114 and the Y-axis GMR elements 121-124 incorporated inthe foregoing magnetic sensor 101. Herein, solid curves represent themagnetic characteristics of the sensing directions of the GMR elements,and dotted curves represent the magnetic characteristics of thenon-sensing directions of the GMR elements.

As shown in FIG. 9, a hysteresis loop cannot be recognized with regardto the sensing directions of the GMR elements 11-14 and 21-24. Inaddition, a hysteresis loop may also be recognized with regard to thenon-sensing directions of the GMR elements 11-14 and 21-24, whereas itdisappears at or in proximity to a ‘zero’ value of the magnetic field;thus, it is possible to improve the resistant characteristics to anintense magnetic field.

FIG. 10 shows that a hysteresis loop may be recognized with regard tothe non-sensing directions of the foregoing GMR elements 111-114 and121-124, wherein it lies in proximity to a ‘zero’ value of the magneticfield; hence, the resistant characteristics to an intense magnetic fieldmust be reduced.

In summary, it is possible to noticeably improve the resistantcharacteristics to an intense magnetic field in the GMR elementsincorporated in the magnetic sensor 1 of the present embodiment, inwhich each of the permanent magnet films 32 is arranged to form aprescribed angle of 45° relative to the longitudinal direction of eachof the magnetoresistive elements 31, compared with the GMR elementsincorporated in the foregoing magnetic sensor 101.

As described above, the magnetic sensor 1 of the present embodiment isproduced in such a way that the X-axis GMR elements 11-14 and the Y-axisGMR elements 21-24 are formed on the quartz substrate 2, wherein themagnetoresistive elements 31 thereof are arranged such that each of themagnetization directions of the pinned layers PD forms a prescribedangle of 45° relative to each of the magnetization directions of thefree layers F. Therefore, even when an intense magnetic field isapplied, it is possible to reliably suppress offset variations of thebridges, which in turn contributes to a noticeable improvement in theresistant characteristics to an intense magnetic field.

According to the manufacturing method of the magnetic sensor 1 of thepresent embodiment, the permanent magnets 45 are arranged at the fourcorners of the quartz substrate 2, which is divided in the subsequentcutting process, in such a way that the adjoining permanent magnets 45differ from each other in polarity, in which a magnetic field is appliedto each permanent magnet film M in the longitudinal direction;therefore, even when an intense magnetic field is applied, it ispossible to reliably suppress offset variations of the bridge circuits.In summary, it is possible to produce the magnetic sensor 1, which cannoticeably improve the resistant characteristics to an intense magneticfield, with ease by simple processes.

The present embodiment uses the plate that has the through holes 43without changing the shapes and distances compared with the foregoingthrough holes 143, in which each of the alignment marks is shifted inposition by a half pitch. Of course, it is possible to use another platein which each of the through holes is shifted in position by a halfpitch. In addition, it is possible to use a plate in which both of theforegoing alignment marks and the new alignment marks each shifted inposition by a half pitch are formed.

The magnet array adapted to the present embodiment is not necessarilylimited to one in which the permanent magnets 45 are adhered to theplate 44 made by the aforementioned quartz glass. That is, it ispossible to use a substrate 46 composed of a Ni₄₂Fe₅₈ alloy, and a metalplate 47 composed of tungsten (W) in which a plurality of through holes43 conforming with the exterior shapes of the permanent magnets 45 areformed, so that the substrate 46 and the metal plate 47 are adheredtogether as shown in FIG. 11A, whereby the permanent magnets 45 arerespectively inserted into the through holes 43.

Similar to the foregoing magnetic sensor 101 in which the quartz glass141 and the plate 151 are fixed together using the fixing members 155such as clips (see FIG. 40), the quartz glass 41 is fixed using thefixing members 155 as shown in FIG. 11B.

In the aforementioned magnet array, both of the Ni₄₂Fe₅₈ alloy andtungsten (W) are close to silicon (Si) in terms of thermal expansioncoefficient; therefore, even when a thermal expansion is caused to occurdue to heating, there is no possibility of causing positional deviationsbetween the substrate 46 and the metal plate 47; hence, it is possibleto improve the positional accuracy of the magnet array. Herein, themetal plate 47 is used as a part of the magnet array and does not needto be removed; hence, it is possible to improve the holding accuracy ofthe permanent magnets 45, and it is therefore possible to manufacturethe magnetic sensor 1 with ease.

2. Second Embodiment

FIG. 12 is a plan view showing a magnetic sensor 50 in accordance with asecond embodiment of the invention, wherein GMR elements are arrangedalong the four sides of a quartz substrate 2, and each of them isconstituted by magnetoresistive elements 31 and permanent magnet films32. The magnetic sensor 50 of the second embodiment differs from themagnetic sensor 1 of the first embodiment in that the longitudinaldirection of each magnetoresistive element 31 lies parallel to theproximate side of the quartz substrate 2.

Specifically, the magnetic sensor 2 comprises the ‘roughlysquare-shaped’ quartz substrate 2 having a prescribed thickness as wellas X-axis GMR elements 51-54 and Y-axis GMR elements 61-64 that areformed on the quartz substrate 2, wherein the X-axis GMR elements 51-54form an X-axis magnetic sensor for detecting a magnetic field in theX-axis direction, and the Y-axis GMR elements 61-64 form a Y-axismagnetic sensor for detecting a magnetic field in the Y-axis direction.

In the above, the X-axis GMR elements 51-54 are paired and respectivelyarranged in proximity to the midpoints of two sides of the quartzsubstrate 2 perpendicular to the X-axis in such a way that the two pairsof them are arranged in parallel with each other. Similarly, the Y-axisGMR elements 61-64 are paired and respectively arranged in proximity tothe midpoints of the other two sides of the quartz substrate 2perpendicular to the Y-axis in such a way that the two pairs of them arearranged in parallel with each other.

Each of the X-axis GMR elements 51-54 and the Y-axis GMR elements 61-64is constituted by magnetoresistive elements 31, each of which is roughlyshaped as a parallelogram and comprises band-shaped spin valve filmsarranged in parallel with each other, and permanent magnet films 32 thatare connected with both ends of the magnetoresistive element 31 in thelongitudinal direction, and each of which is made by a roughlysquare-shaped thin film composed of a hard ferromagnetic substance suchas CoCrPt having a high coercive force and a high squareness ratio,wherein the magnetoresistive elements 31 and the permanent magnet films32 are arranged such that the longitudinal directions thereof conformwith each other.

Each of the magnetoresistive elements 31 is formed such that thelongitudinal direction thereof lies in parallel with the proximate sideof the quartz substrate 2. In addition, each of the permanent magnetfilms 32 is formed such that the longitudinal direction thereof lies inparallel with the proximate side of the quartz substrate 2, wherein the‘paired’ permanent magnet films 32, which are connected with both endsof the same magnetoresistive element 31, are arranged with the samedistance from the proximate side of the quartz substrate 2.

In the above, the magnetization direction of the pinned layer isinclined by 45° relative to the longitudinal direction of themagnetoresistive element 31, whereas the magnetization direction of thepermanent magnet film 32 lies along the longitudinal direction of thepermanent magnet film 32. That is, the magnetization direction of thepinned layer of the magnetoresistive element 31 forms a prescribed angleof 45° relative to the magnetization direction of the permanent magnetfilm 32.

Similar to the magnetic sensor 1 of the first embodiment, the structureof the spin valve film adapted to each of the X-axis GMR elements 51-54and the Y-axis GMR elements 61-64 is identical to the structure of theforegoing spin valve film 131 adapted to each of the X-axis GMR elements111-114 and the Y-axis GMR elements 121-124; hence, the detaileddescription regarding the structure of the spin valve film will beomitted.

In each of the X-axis GMR elements 51-54 and the Y-axis GMR elements61-64, the longitudinal direction of the pinned layer PD of themagnetoresistive element 31 matches the longitudinal direction of thepermanent magnet film 32. Herein, the magnetization direction of thepinned layer PD is inclined by 45° relative to the longitudinaldirection of the magnetoresistive element 31. That is, the magnetizationdirection of the pinned layer PD of the magnetoresistive element 31forms a prescribed angle of 45° relative to the magnetization directionof the permanent magnet film 32.

Next, a manufacturing method of the magnetic sensor 50 will be describedin detail.

The second embodiment is characterized by using two types of magnetarrays. That is, similar to the magnetic sensor 1 of the firstembodiment, spin valve films are formed on a rectangular-shaped quartzglass in order to form permanent magnet films 32 and individual GMRelements.

Next, as shown in FIG. 13, there is prepared a first metal plate 67having a rectangular shape in which a plurality of through holes 43 eachhaving a rectangular-shaped opening are slanted by 45° and are arrangedin parallel with each other, wherein a plurality of bar magnets 68 madeof rectangular-parallelopiped permanent magnets whose cross-sectionalshapes substantially match the opening shapes of the through holes 43are respectively inserted into the through holes 43 in such a way thatthe upper end surfaces thereof are arranged substantially in the sameplane in parallel with the surface of the first metal plate 67, and theadjoining bar magnets 68 differ from each other in polarity.

Thereafter, similar to the first embodiment, there is provided a firstplate made of a transparent quartz glass whose shape substantiallymatches the shape of the first metal plate 67, wherein the upper endsurfaces of the bar magnets 68 that are arranged in parallel with eachother in the magnet array are adhered to the lower surface of the firstplate by using a prescribed adhesive. At this time, alignment marks areused to establish prescribed positioning between the first plate and thebar magnets 68.

Next, the first metal plate 67 is removed so as to produce a magnetarray in which the bar magnets 68 are arranged in parallel with eachother, and the adjoining bar magnets 68 differ from each other inpolarity.

There is arranged a quartz substrate that is brought into contact withthe upper surface of the first plate. That is, a prescribed positioningbetween the aforementioned quartz glass 41 and the first plate isestablished by mutually matching their alignment marks together. Next, aplurality of fixing members such as clips are used to fix the quartzglass 41 and the first plate together.

The aforementioned magnet array in which the bar magnets 68 are arrangedin parallel with each other results in good accuracy because even whenthey are unexpectedly shifted in position and in distance therebetween,the magnetization directions thereof would not be deviated so that nodispersion occurs in an ordering heat treatment.

Similar to the first embodiment, the second embodiment can be designedso as to provide a substrate composed of a Ne₄₂Fe₅₈ alloy, and a metalplate composed of tungsten (W) in which a plurality of through holesconform with the exterior shapes of the bar magnets 68, wherein thesubstrate and the metal plate are adhered together so that the barmagnets 68 are respectively inserted into the through holes.

As the magnet array, it is possible to use various types of magnetarrays, other than the aforementioned magnet array, as follows:

-   (1) A magnet array in which bar magnets each having a different    polarity are alternately arranged.

As shown in FIG. 14A, a dicing saw 72 is used to form a plurality ofslots 73, which are arranged in parallel with each other with aprescribed distance therebetween, on a surface (or a main surface) 71 aof a silicon (Si) substrate 71. Each of the slots 73 has a prescribedwidth that is substantially identical to the width of the bar magnet 68inserted therein and is substantially identical to the width of thedicing saw 72. Similar to the aforementioned magnet array, the distancebetween the adjacent slots 73 is set to half of the length of thediagonal line of the quartz substrate 2.

Then, as shown in FIG. 14B, the bar magnets 68 are respectively insertedinto the slots 73 in such a way that the adjoining bar magnets 68 differfrom each other in polarity. In this case, the bar magnets 68 arearranged and exposed on the surface 71 a of the silicon substrate 71 insuch a way that as shown in FIG. 15, the adjoining bar magnets 68 differfrom each other in polarity, whereby poles N, S, N, . . . aresequentially arranged. As described above, it is possible to produce amagnet array in which the bar magnets 68 each having a differentpolarity are alternately arranged in the silicon substrate 71.

In the aforementioned magnet array, the distance between the adjacentbar magnets 68 is set to half of the length of the diagonal line of thequartz substrate 2. Therefore, when the magnet array is mounted on thequartz glass 41 in such a way that, as shown in FIG. 16, a single barmagnet 68 is arranged to match the diagonal line of each single cell 75(i.e., a region corresponding to the quartz substrate 2 divided in thesubsequent cutting process), its ‘adjoining’ bar magnets 68 arepositioned at opposite corners of the cell 75 to be symmetrical with thediagonal line.

-   (2) A magnet array in which bar magnets of the same polarity are    arranged in parallel with each other.

As shown in FIG. 17A, a dicing saw 72 is used to form a plurality ofslots 73, which are arranged in parallel with each other with aprescribed distance therebetween, on a surface (or a main surface) 77 aof a Ni₄₂Fe₅₈ alloy substrate 77, wherein the slot 73 has a prescribedwidth that is roughly set identical to the width of the bar magnet 68inserted therein. The distance between the ‘adjacent’ slots 73 aresubstantially set identical to the length of the diagonal line of thequartz substrate 2.

Next, as shown in FIG. 17B, the bar magnets 68 are respectively insertedinto the slots 73 of the substrate 77 in such a way that all theadjoining bar magnets 68 have the same polarity. In this case, all thebar magnets 68 are arranged with the same polarity on the surface 77 aof the Ni₄₂Fe₅₈ alloy substrate 77, whereby the same polarity ‘N’appears in turn on the surface 77 a as shown in FIG. 18.

In the above, an intermediate portion of the Ni₄₂Fe₅₈ alloy substrate 77between the adjacent bar magnets 68 having the same polarity ‘N’ on thesurface 77 a has an inverse polarity, that is, polarity ‘S’. That is, itapparently seems as if different polarities N, S, N, . . . aresequentially arranged in a prescribed direction (i.e., a direction fromthe left to the right in FIG. 18) in parallel upon a parallelarrangement of the bar magnets 68 with a prescribed distancetherebetween, which is substantially identical to half of the length ofthe diagonal line of the quartz substrate 2.

As described above, it is possible to produce a magnet array in whichthe bar magnets 68 having the same polarity are arranged in parallelwith each other in the Ni₄₂Fe₅₈ alloy substrate 77.

In the aforementioned magnet array, the distance between the adjacentbar magnets 68 is set to be identical to the length of the diagonal lineof the quartz substrate 2. That is, when the magnet array is mounted onthe quartz glass 41 in such a way that a single bar magnet 68 isarranged on the diagonal line of a single cell 75 as shown in FIG. 19,each of the corners of the cell 75 that lie symmetrically with respectto the diagonal line matches a line segment 76 that is drawn at aposition equally dividing the distance between the adjacent bar magnets68. Herein, each of the positions of the line segments 76 thatrespectively cross the opposite corners of the cell 75 and are drawn tobe symmetric with respect to the diagonal line of the cell 75corresponds to a different polarity (i.e., ‘S’) that differs from thepolarity ‘N’ of the bar magnet 68. That is, it apparently seems as ifmagnets having the polarity ‘S’ are arranged on the corners of the cell75.

In the aforementioned magnet array, it is possible to reliably preventthe bar magnets 68 from attracting each other and falling over or fromunexpectedly rotating by themselves. Therefore, it is possible to fixthe bar magnets 68, which cannot be fixed using a thin metal plate, atprescribed positions with ease and with good accuracy.

Thereafter, the pinning layer PN within the pin layer of themagnetoresistive element 31 is subjected to an ordering heat treatment.

First, as shown in FIG. 20, three bar magnets 68 are arranged with aprescribed distance therebetween to be inclined by 45° relative to aprescribed side of the quartz glass 41 in such a way that the adjoiningbar magnets 68 differ from each other in polarity.

In this case, a prescribed magnetic field is established in a directionfrom one adjacent bar magnet 68 to the other, wherein the magnetic fieldis inclined by 45° relative to the prescribed side of the quartzsubstrate 2, so that a magnetic field is applied in a direction inclinedby 45° with respect to the longitudinal direction of each spin valvefilm M.

Next, the quartz glass 41 and the aforementioned plate are fixedtogether using the fixing members, and are subjected to a heat treatmentunder a vacuum state for four hours at a prescribed temperature rangingfrom 250° C. to 280° C., for example.

Thus, it is possible to perform an ordering heat treatment on thepinning layers of the magnetoresistive elements 31 incorporated in eachof the X-axis GMR elements 51-54 and the Y-axis GMR elements 61-64.Then, similar to the first embodiment, the spin valve layers aresubjected to patterning. As a result, it is possible to produce themagnetic sensor 50 in which the X-axis sensing direction F1 and theY-axis sensing direction F2 lie in the pinned layers P of themagnetoresistive elements 31 as shown in FIG. 21.

Thereafter, as shown in FIG. 22, a magnet array whose constitution issimilar to the constitution of the magnet array used in the firstembodiment is used to magnetize the permanent magnet films 32.

In the above, similar to the first embodiment, the permanent magnets 45are arranged on the four corners of the quartz substrate 2, which isdivided by the subsequent cutting process, in such a way that theadjoining permanent magnets 45 differ from each other in polarity,whereby a magnetic field is established from one permanent magnet 45 ofthe N pole to the other permanent magnet 45 of the S pole. This magneticfield is effected in parallel with each single side of the quartzsubstrate 2; hence, it is possible to establish a magnetic field in adirection substantially matching the longitudinal direction of eachpermanent magnet film 32.

As described above, it is possible to produce the magnetic sensor 50 inwhich the free layers F of the pin layers of the magnetoresistiveelements 31 are initialized in magnetization, and the permanent magnetsfilms 32 are adequately magnetized.

The magnetic sensor 50 of the second embodiment employs the same bridgeconnection adapted to the magnetic sensor 1 of the first embodiment. Inshort, the second embodiment can offer the same effects realized in theaforementioned first embodiment.

3. Third Embodiment

The second embodiment uses the magnet array whose constitution isidentical to the constitution of the magnet array used in the firstembodiment so as to adequately attach the permanent magnets 45 and tomagnetize the permanent magnet films 32. Herein, the magnetization ofthe permanent magnet films 32 can be realized directly using theaforementioned magnet array that is used in the ordering heat treatmentin the second embodiment without changing the arranging positions of themagnets.

In this magnetization, a magnetic field is established along thediagonal line of the quartz substrate 2, which is divided in thesubsequent cutting process, and in a direction inclined by 45° relativeto one side of the quartz substrate 2. Therefore, a magnetic field isapplied to the permanent magnet film 32 whose longitudinal direction isset in parallel with one side of the quartz substrate 2 in a direction45° inclined relative to the longitudinal direction of the permanentmagnet 32.

In this case, the terminal end of the free layer F is initialized in adirection identical to the magnetization direction of the permanentmagnet film 32. In general, the initialization direction of the freelayer F is aligned in the longitudinal direction due to shapeanisotropy. For this reason, each of the GMR elements is initialized inmagnetization along the longitudinal direction thereof, which is set inparallel with a prescribed side of the quartz substrate 2.

As described above, it is possible to produce a magnetic sensor of thethird embodiment in which the free layer F of the magnetoresistiveelement 31 is initialized in magnetization, and the permanent magnetfilm 32 is adequately magnetized.

The third embodiment allows a small loss at the terminal end of the freelayer F, which may slightly deteriorate the sensitivity compared withthe second embodiment; however, the third embodiment is designed in sucha way that the magnetization direction is set similar to the firstembodiment; hence, it is possible to noticeably reduce offset variationseven when an intense external magnetic field is applied to the magneticsensor.

4. Fourth Embodiment

FIG. 23 is a plan view showing a magnetic sensor in accordance with afourth embodiment of the invention, wherein, similar to theaforementioned embodiments, a magnetic sensor 81 of the fourthembodiment is constituted using GMR elements and permanent magnet filmsformed on a quartz substrate 2. Herein, the magnetic sensor 81 differsfrom the magnetic sensor 50 of the second embodiment, in which theX-axis GMR elements 51-52 are arranged in parallel with each other inproximity to the midpoint of one side of the quartz substrate 2 lying inthe negative direction of the X-axis, and the Y-axis GMR elements 63-64are arranged in parallel with each other in proximity to the midpoint ofthe other side of the quartz substrate 2 lying in the negative directionof the Y-axis, such that in order to cancel the sensitivities realizedby the X-axis GMR elements 51-52 and the Y-axis GMR elements 63-64, theyare arranged substantially in the center of the quartz substrate 2 andare inclined by 45° relative to a prescribed side of the quartzsubstrate 2.

In the manufacture of the magnetic sensor 81, the pinning layers of themagnetoresistive elements 31 are subjected to an ordering heat treatmentin which the quartz glass 41 is heated for four hours in a vacuum stateat a prescribed temperature ranging from 250° C. to 280° C., forexample, wherein a magnetic field is applied in a direction parallel tothe X-axis GMR elements 51-52 and the Y-axis GMR elements 63-64. Thatis, as shown in FIG. 24, it is preferable that a magnetic field havinguniform intensity be applied along the longitudinal directions of theX-axis GMR elements 51-52 and the Y-axis GMR elements 63-64 and in adirection from the lower left to the upper right.

Similar to the aforementioned embodiments, the magnetic sensor 81 issubjected to magnetization by fixing the quartz glass and platetogether.

As described above, it is possible to initialize the free layers F ofthe magnetoresistive elements 31 incorporated in the X-axis GMR elements51-54 and the Y-axis GMR elements 61-64 and to adequately magnetize thepermanent magnet films 32. Thus, it is possible to produce the magneticsensor 81 in which the pinned layers PD of the magnetoresistive elements31 and the permanent magnet films 32 are adequately magnetized.

As shown in FIG. 25, the aforementioned magnetic sensor 81 presents anX-axis sensing direction F1 and a Y-axis sensing direction F2 withrespect to the pinned layers PD of the magnetoresistive elements 31,except for the magnetoresistive elements 31 incorporated in the GMRelements 51-52 and 63-64 arranged substantially in the center of thequartz substrate 2.

The bridge connections of the GMR elements incorporated in the magneticsensor 81 are identical to those of the magnetic sensor 1 of the firstembodiment. Therefore, the fourth embodiment can offer effects similarto those of the first embodiment.

5. Fifth Embodiment

The fifth embodiment is basically identical to the fourth embodiment butis characterized in that the aforementioned magnet array is not used buta uniform magnetic field is applied in order to magnetize the permanentmagnet films 32 similar to the aforementioned ordering heat treatment.

Herein, the magnetization of the permanent magnet films 32 will bedescribed in detail.

That is, a uniform magnetic field whose intensity is uniform is appliedin a direction from the lower left to the upper right in FIG. 24 similarto the aforementioned ordering heat treatment.

With respect to the X-axis GMR elements 53-54, which are arranged inparallel with one side of the quartz glass 41, and the Y-axis GMRelements 61-62, which are arranged in parallel with the other side ofthe quartz substrate 41, a magnetic field is applied along the diagonalline of the quartz substrate 2, which is divided by the subsequentcutting process, and in a direction inclined by 45° relative to eachside of the quartz substrate 2. That is, a magnetic field is applied toeach of the permanent magnet films 32 whose longitudinal directions areparallel to prescribed sides of the quartz substrate 2 in a directioninclined by 45° relative to each of the longitudinal directions of thepermanent magnet films 32.

The terminal end of the free layer F is initialized in a directionidentical to the magnetization direction of the permanent magnet 32,wherein the free layer F is magnetized in the longitudinal directionthereof due to shape anisotropy thereof, so that the free layer F isinitialized in magnetization in the longitudinal direction of thecorresponding GMR element, that is, along the prescribed side of thequartz glass 41.

The fifth embodiment allows a small loss at the terminal end of the freelayer F, which may slightly reduce the sensitivity compared with thesensitivity of the magnetic sensor of the second embodiment; however,the fifth embodiment is designed to realize the same magnetizationdirection(s) actualized in the first embodiment; hence, it is possibleto noticeably reduce offset variations even when an intense externalmagnetic field is applied to the magnetic sensor.

FIG. 43 shows the results of a comparison between the magnetic sensor ofthis invention (i.e., Embodiments 1-5) and the foregoing magnetic sensor(i.e., Comparative Example), wherein Embodiment 1 corresponds to themagnetic sensor 1 of the first embodiment; Embodiment 2 corresponds tothe magnetic sensor 50 of the second embodiment; Embodiment 3corresponds to the magnetic sensor of the third embodiment; Embodiment 4corresponds to the magnetic sensor 81 of the fourth embodiment; andEmbodiment 5 corresponds to the magnetic sensor of the fifth embodiment.

FIG. 43 shows that compared with the Comparative Example, all themagnetic sensors of Embodiments 1-5 are superior in the resistantcharacteristics to an intense magnetic field. In each of Embodiments 1-5compared with the Comparative Example, it is possible to reduce offsetvariations after exposure of a magnetic field of 100 Oe, which shows theresistant characteristics to an intense magnetic field.

Each of Embodiments 1-5 may be reduced in sensitivity compared with theComparative Example in which the longitudinal direction of the GMRelement crosses at a right angle to the magnetization direction of thepinned layer realized in the ordering heat treatment; however, it can besaid that each of them presents the good resistant characteristics to anintense magnetic field.

In addition, it can be said that, compared with Embodiments 2 and 4 inwhich the magnetization direction of the permanent magnet film differsfrom the magnetization direction of the pinned layer realized in theordering heat treatment, Embodiments 1, 3, and 5, in which themagnetization direction of the permanent magnet film is identical to themagnetization direction realized in the ordering heat treatment, canoffer the good resistant characteristics to an intense magnetic field.

In each of Embodiments 1, 3 and 5 in which the magnetization directionof the permanent magnet film does not match the longitudinal directionof the GMR element (i.e., the longitudinal direction of the free layer),the terminal end of the free layer is magnetized in the magnetizationdirection of the permanent magnet film; hence, a small loss may occur soas to slightly reduce the sensitivity. However, variation ratios withrespect to the sensitivity are small because of the ‘good’ resistantcharacteristics to an intense magnetic field.

As described heretofore, this invention has a variety of effects andtechnical features, which will be described below.

-   (1) A magnetic sensor of this invention is characterized in that the    magnetization direction of a pinned layer of a magnetoresistive    element forms a prescribed angle of 45° relative to the longitudinal    direction of the magnetoresistive element; therefore, even when an    intense magnetic field is applied, it is possible to reliably    suppress offset variations of the bridge connections of the GMR    elements; hence, it is possible to noticeably improve the resistant    characteristics to an intense magnetic field.-   (2) In addition, it is possible to modify the magnetic sensor in    such a way that the magnetization direction of a pinned layer of a    magnetoresistive element forms a prescribed angle of 45° relative to    the magnetization direction of a permanent magnet film, whereby even    when an intense magnetic field is applied, it is possible to    reliably suppress offset variations of the bridge connections of the    GMR elements; hence, it is possible to noticeably improve the    resistant characteristics to an intense magnetic field.-   (3) According to a manufacturing method of the magnetic sensor of    this invention, an ordering heat treatment is performed using a    magnet array in which a plurality of permanent magnets are arranged    in such a way that adjoining permanent magnets differ from each    other in polarity, wherein a substrate is arranged on the magnet    array such that the permanent magnets are positioned to respectively    or selectively match the four corners of a cell within the    substrate, which is then heated. Herein, the permanent magnet films    are magnetized by arranging the substrate on the magnet array    without changing the relative positional relationship therebetween;    therefore, it is possible to initialize the free layer of the    magnetoresistive element and to magnetize the permanent magnet film    with ease. As a result, it is possible to produce the magnetic    sensor, in which the magnetization direction of the magnetoresistive    element forms a prescribed angle of 45° relative to the    magnetization direction of the permanent magnet film, by simple    processes with ease.-   (4) It is possible to modify the manufacturing method in such a way    that the ordering heat treatment is performed by heating the    substrate in which the magnetization direction of the pinned layer    substantially matches the diagonal line of the cell within the    substrate, wherein the permanent magnet films are magnetized by    arranging the substrate on the magnet array in which adjoining    permanent magnets are arranged to differ from each other in    polarity, whereby it is possible to initialize the free layer of the    magnetoresistive element and to magnetize the permanent magnet film    with ease. Thus, it is possible to produce the magnetic sensor, in    which the magnetization direction of the pinned layer of the    magnetoresistive element forms a prescribed angle of 45° relative to    the magnetization direction of the permanent magnet film, by simple    processes with ease.-   (5) It is possible to further modify the manufacturing method in    such a way that the ordering heat treatment is performed by heating    the substrate in which the magnetization direction of the pinned    layer matches the diagonal line of the cell within the substrate,    wherein the permanent magnet films are magnetized by arranging the    substrate such that the magnetization direction of the pinned layer    substantially matches the diagonal line of the cell, whereby it is    possible to initialize the free layer of the magnetoresistive    element and to magnetize the permanent magnet film with ease. Thus,    it is possible to produce the magnetic sensor, in which the    magnetization direction of the pinned layer of the magnetoresistive    element forms a prescribed angle of 45° relative to the    magnetization direction of the permanent magnet film, by simple    processes with ease.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiments are therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all changes that fall within metesand bounds of the claims, or equivalents of such metes and bounds aretherefore intended to be embraced by the claims.

1. A manufacturing method of a magnetic sensor, comprising the steps of:forming a plurality of permanent magnet films on a substrate; forming aplurality of spin valve films each composed of a pinning layer, a pinnedlayer, and a free layer; subjecting the pinning layer to an orderingheat treatment; patterning the plurality of spin valve layers to form aplurality of magnetoresistive elements, which are arranged in such a waythat the plurality of permanent magnet films are paired and arerespectively connected to both ends of the magnetoresistive elements;and magnetizing the plurality of permanent magnet films, wherein theordering heat treatment is performed using a magnet array in which aplurality of permanent magnets are respectively arranged in conformitywith four corners of a cell of the substrate such that adjoiningpermanent magnets differ from each other in polarity, and then thesubstrate is heated, and wherein the plurality of permanent magnet filmsare magnetized by arranging the substrate on the magnet array withoutchanging a relative positional relationship therebetween.